JP2019149784A - Array antenna - Google Patents

Abstract

To provide an array antenna which can realize a desired beam width and directivity.SOLUTION: An array antenna comprises a power-supply line having first and second branch-line parts (12a, 12b) adjacent to each other, and each extending along one direction and having a plurality of radiation element parts (13a-13l), and a coupled line part (11). The plurality of radiation element parts that the first branch-line part has are disposed on one side of the first branch-line part. The plurality of radiation element parts that the second branch-line part has are disposed on a side of the second branch-line part opposite to the one side. A distance from a coupling part (p1) of the first and second branch-line parts and the coupled line part to the radiation element part closest to the coupling part, which is one of the plurality of radiation element parts of the first branch-line part, is larger, in electrical length, than a distance from the coupling part to the radiation element part closest to the coupling part, which is one of the plurality of radiation element parts of the second branch-line part, by (2n-1)λ/2 (λ is a wavelength, and n is a natural number).SELECTED DRAWING: Figure 1

Description

  The present invention relates to the technical field of array antennas.

  As this type of antenna, for example, a planar array antenna having a feeding strip line extending linearly and a plurality of radiating antenna elements protruding vertically from the line has been proposed (see Patent Document 1). An auxiliary antenna is composed of two element antennas arranged at a predetermined interval on the same plane orthogonal to the main lobe direction of the main antenna, and a high-frequency signal from the element antenna has the same amplitude and reverse at the reception target frequency. A technique of synthesizing with a phase has been proposed (see Patent Document 2).

JP 2001-111330 A JP, 2015-010823, A

  In this type of antenna, the beam width and directivity are used as indices indicating the performance of the antenna. However, the techniques described in Patent Documents 1 and 2 have a technical problem that it is difficult to design an antenna so that the beam width and directivity become a desired beam width and directivity.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an array antenna that can realize a desired beam width and directivity relatively easily.

  An array antenna according to an aspect of the present invention is adjacent to each other and extends along one direction, and has a plurality of radiating element portions, a first branch line portion and a second branch line portion, and the first branch A plurality of radiating element units included in the first branch line unit on one side of the first branch line unit. The plurality of radiating element portions included in the second branch line portion are disposed on a side opposite to the one side of the second branch line portion, and the first branch line portion and the first branch line portion The distance from the coupling part between the two branch line part and the coupling line part to the radiating element part closest to the coupling part among the plurality of radiating element parts included in the first branch line part is from the coupling part, Among the plurality of radiating element portions of the second branch line portion Serial than the distance to the nearest radiating element to the coupling part, in electrical length (2n-1) λ / 2 long (the lambda wavelength, n represents a natural number) is that.

It is a top view which shows the array antenna which concerns on 1st Embodiment. It is a characteristic view which shows an example of the characteristic of the array antenna which concerns on 1st Embodiment. It is a top view which shows the array antenna which concerns on the modification of 1st Embodiment. It is a top view which shows the array antenna which concerns on 2nd Embodiment. It is a characteristic view which shows an example of the characteristic of the array antenna which concerns on 2nd Embodiment. It is a top view which shows the array antenna which concerns on 3rd Embodiment. It is a top view which shows the array antenna which concerns on 4th Embodiment. It is a characteristic view which shows an example of the characteristic of the array antenna which concerns on each of 2nd thru | or 4th embodiment. It is a top view which shows the array antenna which concerns on 5th Embodiment. It is a characteristic view which shows an example of the characteristic of the array antenna which concerns on 5th Embodiment.

  An array antenna according to an embodiment will be described with reference to the drawings.

<First Embodiment>
The array antenna according to the first embodiment will be described with reference to FIGS.

(Constitution)
An overview of the array antenna according to the first embodiment will be described with reference to FIG. FIG. 1 is a plan view showing an array antenna according to the first embodiment. Note that the dielectric substrate and the ground plane are not shown. The same applies to FIGS. 3, 4, 6, 7, and 9.

  In FIG. 1, an array antenna 1 is an array antenna for horizontal polarization. The array antenna 1 includes branch line portions 12a and 12b that are adjacent to each other and extend in one direction (the vertical direction in the drawing), and a coupled line portion 11 that couples the branch line portions 12a and 12b. The coupled line portion 11 and the branch line portions 12 a and 12 b constitute a feed line of the array antenna 1. In the present embodiment, “branching line portions 12a and 12b adjacent to each other” means “branching line portions 12a and 12b adjacent to each other without interposing another feeding line (or branch line portion)”. It is preferable to mean.

  The branch line portion 12a includes a plurality of radiating element portions 13a, 13b, 13c, 13d, 13e, and 13f that protrude in a branch shape on the opposite side of the branch line portion 12b in the direction intersecting with the one direction. Similarly, the branch line portion 12b includes a plurality of radiating element portions 13g, 13h, 13i, 13j, 13k, and 13l protruding in a branch shape on the opposite side to the branch line portion 12a in a direction intersecting with the one direction. Have. Particularly in the present embodiment, the array antenna 1 has a distance from the coupling part p1 between the branch line parts 12a and 12b and the coupling line part 11 to the radiating element part 13f is larger than a distance from the coupling part p1 to the radiating element part 13l. The electrical length is (2n-1) λ / 2 longer (n is a natural number). The “electrical length” is a length based on an electrical phase change amount, and a length at which the phase changes by 360 ° corresponds to one wavelength.

  In each of the branch line portions 12a and 12b, power (hereinafter referred to as “traveling wave” as appropriate) from the coupling portion p1 and power (hereinafter referred to as “reflected wave” as appropriate) from the reflection end toward the coupling portion p1. A standing wave is generated. Each of the radiating element portions 13a, 13b, 13c, 13d, 13e, and 13f is disposed at a portion corresponding to a node of a standing wave generated in the branch line portion 12a. Similarly, each of the radiating element portions 13g, 13h, 13i, 13j, 13k, and 13l is disposed at a portion corresponding to a node of a standing wave generated in the branch line portion 12b.

  Part of the electric power input to the coupled line unit 11 is radiated by being sequentially coupled to each of the radiating element units 13a, 13b, 13c, 13d, 13e, and 13f via the branch line unit 12a (that is, each radiation) Radio waves are emitted from the element part). Further, the other part of the electric power input to the coupled line unit 11 is sequentially coupled and radiated to each of the radiating element units 13g, 13h, 13i, 13j, 13k, and 13l via the branch line unit 12b.

(Array antenna beam width)
For example, an array antenna of the type described in Patent Document 1 includes a feed line that is formed on a dielectric substrate and extends in a straight line, and a plurality of radiations that are directly connected to the feed line and project in a branch shape. It is comprised by an element part. The beam width of the array antenna is the width between the left and right radiating element parts of the array antenna (for example, the center of the radiating element part projecting to one side of the feed line and the opposite side of one side of the feed line) It varies depending on the distance from the center of the radiating element section. Specifically, the beam width is narrowed (that is, the directivity is improved) as the width between the radiating element portions is increased. On the other hand, the narrower the width between the radiating element portions, the wider the beam width (that is, the directivity decreases).

  By the way, the propagation speed of the electromagnetic wave in the medium (dielectric) is determined by the dielectric constant and magnetic permeability of the medium. Since the relative magnetic permeability of the dielectric is approximately 1, the size of the radiating element formed on the dielectric substrate is mainly determined according to the dielectric constant of the dielectric substrate. For this reason, if the dielectric constant of the dielectric substrate is changed, the size of the radiating element portion can be changed. That is, if the dielectric constant of the dielectric substrate is changed, the beam width can be changed by changing the width between the radiating element portions.

  However, since the dielectric substrate needs to satisfy electrical performance such as dielectric constant and loss, and mechanical performance such as strength and thermal expansion coefficient, it is not easy to change the material and the mixing ratio. However, it is difficult to change the dielectric constant of the dielectric substrate so as to obtain a desired beam width. Therefore, it is difficult to change the size of the radiating element portion so as to obtain a desired beam width.

  The array antenna 1 includes branch line portions 12a and 12b as part of a feed line. Therefore, if the distance between the branch line portions 12a and 12b is changed, the radiating element portion is not changed without changing the size of the radiating element portions 13a to 13l (that is, without changing the dielectric constant of the dielectric substrate). The width between can be changed.

(Characteristics of array antenna)
Next, the characteristics of the array antenna 1 will be described with reference to FIG. FIG. 2 is a characteristic diagram showing an example of the characteristics of the array antenna according to the first embodiment. The solid line in FIG. 2 indicates the characteristics of the array antenna 1 (here, horizontal plane directivity). The dotted line in FIG. 2 indicates the characteristics of an array antenna according to a comparative example in which the feed line does not have a branch line portion (for example, an array antenna of the type described in Patent Document 1).

  In FIG. 2, near 0 degrees, the gain of the array antenna 1 (see solid line) is larger than the gain of the array antenna according to the comparative example (see dotted line). On the other hand, in the region where the angle is relatively large, the gain of the array antenna 1 is significantly smaller than the gain of the array antenna according to the comparative example. That is, it can be said that the array antenna 1 has a narrowed beam width or improved directivity compared to the array antenna according to the comparative example.

  In FIG. 2, the characteristics of the array antenna 1 indicated by the solid line are asymmetrical because the left and right radiating element portions are offset vertically and there is a difference in the left and right excitation distributions. it is conceivable that.

(Technical effect)
According to the array antenna 1, by changing the distance between the branch line portions 12a and 12b, a desired beam width and directivity can be realized without changing the size of the radiating element portions 13a to 13l.

  An array antenna may be used for in-vehicle radar, for example. When a radar is mounted on a vehicle, it is often arranged on the back side of an emblem, a bumper, or other resin cover, for example. Here, the transmission characteristics of the electromagnetic wave resin material differ depending on the polarization. Specifically, when the inclination of the resin material is relatively small (that is, when the resin material stands at an angle perpendicular to the ground), the horizontal polarization is more horizontal in the horizontal plane than the vertical polarization. It is known that transmission attenuation in the wide-angle direction is small. On the other hand, an array antenna for horizontally polarized waves tends to radiate electromagnetic waves in the lateral direction, which causes a problem that the directivity pattern is disturbed.

  However, the array antenna 1 is an array antenna for horizontally polarized waves, but by changing the distance between the branch line portions 12a and 12b, a desired beam width is realized, and radiation of electromagnetic waves in the lateral direction is suppressed. Thus, the disturbance of the directivity pattern can be improved. For this reason, according to the array antenna 1, it is possible to realize an on-vehicle radar using horizontally polarized waves that is excellent in the transmission characteristics of the resin material on the front surface of the on-vehicle radar.

<Modification>
A modification of the array antenna 1 according to the first embodiment will be described with reference to FIG. FIG. 3 is a plan view showing an array antenna according to a modification of the first embodiment.

  In FIG. 3 (a), the array antenna 1 'is configured such that the widths of the portions 14a and 14b corresponding to λ / 4 in electrical length from the reflection ends of the branch line portions 12a and 12b are the widths of the other portions. It is formed to be wider. If comprised in this way, the electric energy radiated | emitted from the reflection end of each branch line part 12a and 12b can be suppressed.

  Further, as shown in FIG. 3B, the lengths of the branch line portions 12a and 12b may be the same (or the positions of the reflection ends may be the same).

Second Embodiment
A second embodiment according to the array antenna will be described with reference to FIGS. The second embodiment is the same as the first embodiment described above except that the shape of the array antenna is partially different. Therefore, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and the same reference numerals are given to the common portions on the drawings, and only the differences are basically illustrated in FIGS. 4 and 5. The description will be given with reference.

(Constitution)
An overview of the array antenna according to the second embodiment will be described with reference to FIG. FIG. 4 is a plan view showing an array antenna according to the second embodiment.

  In FIG. 4, the array antenna 2 includes a connection line portion 15 that connects the side opposite to the coupling portion p1 of each of the branch line portions 12a and 12b. The coupled line portion 11, the branch line portions 12 a and 12 b, and the connection line portion 15 constitute a feed line for the array antenna 2.

  In the array antenna 1 according to the first embodiment, each radiating element portion is arranged at a portion corresponding to a node of a standing wave generated by a traveling wave and a reflected wave. In the array antenna 2 according to the present embodiment, the branching line portions 12a and 12b and the connection line portion 15 are connected to the nodes of standing waves generated by the waves related to the power traveling clockwise and the waves related to the power traveling counterclockwise. Each radiating element part is arrange | positioned in the part corresponded to. Hereinafter, the branch line portions 12a and 12b and the connection line portion 15 are appropriately referred to as “annular line portions (12a, 12b, 15)”.

(Characteristics of array antenna)
Next, the characteristics of the array antenna 2 will be described with reference to FIG. FIG. 5 is a characteristic diagram showing an example of the characteristics of the array antenna according to the second embodiment. The solid line in FIG. 5 indicates the characteristics of the array antenna 2 (here, horizontal plane directivity). The dotted line in FIG. 5 indicates the characteristics of the array antenna 1.

  In the array antenna 2 (see the solid line), the left-right asymmetry of the horizontal plane directivity is improved compared to the array antenna 1 (see the dotted line). This is considered that the difference between the left and right excitation distributions is improved by connecting the left and right feeder lines in a ring shape.

(Technical effect)
Also in the array antenna 2, by changing the distance between the branch line portions 12a and 12b (in other words, by changing the oblong flatness formed by the branch line portions 12a and 12b and the connection line portion 15). The desired beam width and directivity can be realized without changing the size of the radiating element portions 13a to 13l.

<Third Embodiment>
A third embodiment according to the array antenna will be described with reference to FIG. The third embodiment is the same as the second embodiment described above except that the shape of the array antenna is partially different. Accordingly, the description of the third embodiment that is the same as that of the second embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only the points that are basically different are described with reference to FIG. explain.

(Constitution)
An overview of the array antenna according to the third embodiment will be described with reference to FIG. FIG. 6 is a plan view showing an array antenna according to the third embodiment.

  In FIG. 6, the array antenna 3 includes a stub 16 having a function equivalent to that of a λ / 4 short-circuited (short) stub connected to the connection line portion 15. The stub 16 may be a stub that is short-circuited with the ground plane using a via (through hole), or may be a stub that functions in the same way as a short-circuit stub without using a via. In FIG. 6, the T-type stub is drawn as an example of the stub 16 having the same function as the λ / 4 short-circuit stub. In the T-type stub, a line having an electrical length of λ / 4 extends from the connection line portion 15, and a land having a size equivalent to a short circuit in the line connection portion is connected to the end. However, the stub 16 is not limited to the T-type stub, and various existing aspects can be applied. However, from the viewpoint of manufacturing the array antenna 3, the stub 16 is preferably a vialess stub.

(Technical effect)
In the bent part of the feed line such as the connection line part 15, unnecessary radiation of electric power is likely to occur. This unnecessary radiation of power becomes more prominent as the radius of curvature of the bent portion is smaller, which causes the directivity to be disturbed. According to the array antenna 3, unnecessary radiation of power from the connection line portion 15 can be suppressed by connecting the stub 16 to the connection line portion 15.

<Fourth embodiment>
A fourth embodiment of the array antenna will be described with reference to FIGS. The fourth embodiment is the same as the third embodiment described above except that the shape of the array antenna is partially different. Accordingly, the description of the fourth embodiment that is the same as that of the third embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only FIGS. 7 and 8 are basically different only. The description will be given with reference.

(Constitution)
An outline of the array antenna according to the fourth embodiment will be described with reference to FIG. FIG. 7 is a plan view showing an array antenna according to the fourth embodiment.

  In FIG. 7, the array antenna 4 includes an impedance matching stub 17 connected to the coupled line portion 11. Since various existing modes can be applied to the impedance matching method, a detailed description thereof will be omitted. The arrangement position and size of the stub 17 change according to the impedance of the array antenna 4.

(Technical effect)
The influence of the annular line portions (12a, 12b, 15) of the array antennas 2, 3, and 4 on the array antenna will be described with reference to FIG. FIG. 8 is a characteristic diagram showing an example of the characteristics of the array antenna according to each of the second to fourth embodiments. The upper part of FIG. 8 is a Smith chart. The lower part of FIG. 8 is a graph showing the relationship between frequency and return loss (reflection coefficient). FIG. 8A is a Smith chart of the array antenna 2 according to the second embodiment, and a graph showing the relationship between frequency and return loss. FIG. 8B is a Smith chart of the array antenna 3 according to the third embodiment, and a graph showing the relationship between frequency and return loss. FIG. 8C is a Smith chart of the array antenna 4 according to the fourth embodiment, and a graph showing the relationship between the frequency and the return loss.

  In the array antenna 2, the reactance component is mainly changed by the ring-shaped line portions (12 a, 12 b, 15), the impedance is shifted, and a frequency at which the return loss is reduced as shown in FIG. It deviates from the frequency (here, 76.5 GHz (gigahertz)). Since the stub 16 does not change the reactance of the annular line portions (12a, 12b, 15) of the array antenna 3, the array antenna 3 including the stub 16 also has a small return loss as shown in FIG. The resulting frequency remains deviated from the desired frequency.

  In the array antenna 4 including the impedance matching stub 17, the impedance shift caused by the annular line portions (12 a, 12 b, 15) is eliminated, and as shown in FIG. 8C, the return loss at a desired frequency is achieved. Can be reduced.

  The array antenna 1 according to the first embodiment may also be provided with an impedance matching stub 17.

<Fifth Embodiment>
A fifth embodiment of the array antenna will be described with reference to FIGS. The fifth embodiment is the same as the first embodiment described above except that the shape of the array antenna is partially different. Accordingly, the description of the fifth embodiment that is the same as that of the first embodiment is omitted, and common portions in the drawings are denoted by the same reference numerals, and only the points that are basically different are shown in FIGS. 9 and 10. The description will be given with reference.

(Constitution)
The outline of the array antenna according to the fifth embodiment will be described with reference to FIG. FIG. 9 is a plan view showing an array antenna according to the fifth embodiment.

  In FIG. 9A, the branch line portion 12a of the array antenna 5 has a plurality of radiating elements protruding in a direction intersecting with one direction (here, the vertical direction of the paper) and branching toward the branch line portion 12b. Part. Similarly, the branch line portion 12b has a plurality of radiating element portions protruding in a branch shape on the branch line portion 12a side in a direction intersecting with the one direction.

  In the array antenna 5, the reflection ends of the branch line portions 12a and 12b are formed wider than the other portions, but the shape of the reflection ends is not limited to this. Moreover, the opposite side to the connection part p1 of each branch line part 12a and 12b may be connected by the connection line part 15, as shown in FIG.9 (b). Although the array antenna 5 ′ shown in FIG. 9B includes the stub 16, the stub 16 may not be provided. Further, the array antenna 5 ′ may include a stub for impedance matching.

(Characteristics of array antenna)
Next, the characteristics of the array antenna 5 will be described with reference to FIG. FIG. 10 is a characteristic diagram showing an example of the characteristics of the array antenna according to the fifth embodiment. The solid line in FIG. 10 indicates the characteristics of the array antenna 5 (here, horizontal plane directivity). The dotted lines in FIG. 10 indicate the characteristics of an array antenna according to a comparative example in which the feed line does not have a branch line portion (for example, the array antenna described in Patent Document 1).

  In FIG. 10, near 0 degrees, the gain of the array antenna 5 (see solid line) is smaller than the gain of the array antenna according to the comparative example (see dotted line). On the other hand, in the region where the angle is relatively large, the gain of the array antenna 5 is larger than the gain of the array antenna according to the comparative example. That is, it can be said that the array antenna 5 has a wider beam width than the array antenna according to the comparative example.

(Technical effect)
According to the array antennas 5 and 5 ', by changing the distance between the branch line portions 12a and 12b, a desired beam width and directivity can be realized without changing the size of the radiating element portion.

  Various aspects of the invention derived from the embodiments and modifications described above will be described below.

  An array antenna according to an aspect of the invention includes a first branch line portion and a second branch line portion that are adjacent to each other and extend along one direction, and each have a plurality of radiating element portions, and the first branch line. And a plurality of radiating element units included in the first branch line unit are arranged on one side of the first branch line unit. The plurality of radiating element portions included in the second branch line portion are disposed on the side opposite to the one side of the second branch line portion, and the first branch line portion and the second branch line portion are provided. The distance from the coupling part between the branch line part and the coupling line part to the radiating element part closest to the coupling part among the plurality of radiating element parts included in the first branch line part is from the coupling part to the first Front of a plurality of radiating element sections included in the two-branch line section Than the distance to the nearest radiating element to the coupling part, in electrical length (2n-1) λ / 2 long (the lambda wavelength, n represents a natural number) is that. In the above-described embodiment, the branch line portions 12a and 12b correspond to an example of the first and second branch line portions, and the coupled line portion 11 corresponds to an example of the coupled line portion.

  The beam width and directivity of the array antenna depend on the width between the radiating element portions in the direction intersecting with the direction in which the feed line extends. As a method of changing the width between the radiating element portions, it is conceivable to change the size of the radiating element portion. However, in order to change the size of the radiating element portion, it is necessary to change the dielectric constant by changing the material and the mixing ratio of the dielectric substrate on which the array antenna is disposed, which is not practical.

  The array antenna includes a first branch line portion and a second branch line portion that are adjacent to each other and extend along one direction as a part of the feed line portion. The distance between the first branch line portion and the second branch line portion can be arbitrarily changed. For this reason, according to the array antenna, by changing the distance between the first branch line portion and the second branch line portion, the width between the radiating element portions can be arbitrarily set without changing the size of the radiating element portion. Can be changed. Therefore, according to the array antenna, a desired beam width and directivity can be realized relatively easily.

  One aspect of the array antenna includes a connection portion that connects opposite sides of the first branch line portion and the second branch line portion opposite to the coupling portion. In the above-described embodiment, the connection line portion 15 corresponds to an example of a connection portion. According to this aspect, for example, the left-right symmetry of the horizontal plane directivity related to the array antenna can be improved.

  In this aspect, the connecting portion may include a stub having the same function as the λ / 4 short-circuit stub. If comprised in this way, the unnecessary radiation | emission of the electric power from a connection part can be suppressed. In the above-described embodiment, the stub 16 corresponds to an example of a stub having a function equivalent to that of a λ / 4 short-circuit stub.

  Another aspect of the array antenna is that the coupled line portion has a stub for impedance matching. In the above-described embodiment, the stub 17 corresponds to an example of a stub for impedance matching. According to this aspect, the impedance related to the array antenna can be easily matched.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. An array antenna with such a change is also applicable. Moreover, it is included in the technical scope of the present invention.

  1, 1 ', 1 ", 2, 3, 4, 5, 5' ... array antenna, 11 ... coupled line section, 12a, 12b ... branch line section, 13a, 13b, 13c, 13d, 13e, 13f, 13g , 13h, 13i, 13j, 13k, 13l... Radiating element portion, 15... Connection line portion, 16... Stub having the same function as the λ / 4 short-circuit stub, 17.

Claims (4)

The first branch line section and the second branch line section, which are adjacent to each other and extend along one direction and each have a plurality of radiating element sections, are coupled to the first branch line section and the second branch line section. A feed line having a coupling line section to
The plurality of radiating element portions of the first branch line portion are disposed on one side of the first branch line portion,
The plurality of radiating element portions of the second branch line portion are disposed on the side opposite to the one side of the second branch line portion,
From the coupling part of the first branch line part and the second branch line part and the coupling line part to the radiation element part closest to the coupling part among the plurality of radiation element parts of the first branch line part The distance is (2n-1) λ / in electrical length, rather than the distance from the coupling portion to the radiating element portion closest to the coupling portion among the plurality of radiating element portions of the second branch line portion. 2 long (λ is wavelength, n is a natural number)
An array antenna characterized by that.   The array antenna according to claim 1, further comprising a connection portion that connects opposite sides of the first branch line portion and the second branch line portion opposite to the coupling portion.   The array antenna according to claim 2, wherein a stub having a function equivalent to a λ / 4 short-circuited stub is provided in the connection portion.   4. The array antenna according to claim 1, wherein the coupling line portion includes a stub for impedance matching. 5.